If it were me, I would have a 2-step process (two separate buttons):
Create the PDF: Use the integrations DocsAutomator or PDFMonkey for this.
Send a message on Whatsapp: You can google it, you can create a URL that will automatically open Whatsapp (itβs something like βhttps://wa.meβ etc.), go to a profile and populate a message. You could include the link to the PDF in this message. This will require cleaning up the phone number and putting everything together in a template column.